The present invention relates to a new and improved amorphous metal alloy strip material and a method of making such strip material. More particularly, the metal alloy strip of the present invention has a width greater than about one inch, a thickness less than about 0.003 inch and consists essentially of 77-80% iron, 12-16% boron and 5-10% silicon, based on atomic percentages. The strip material of the present invention exhibits improved magnetic and physical properties.
With the increased research and development activity in the area of amorphous strip materials, it has become apparent that certain amorphous strip materials may possess the magnetic and physical properties that would enhance the use of such materials in electrical applications such as transformers, generators or electric motors. The use of amorphous strip material in a laminated article for electrical applications is disclosed by the Assignee of the present invention in U.S. patent application Ser. No. 073,812, filed Sep. 10, 1979 now U.S. Pat. No. 4,277,530.
An established alloy composition for strip material used in transformers is Fe80B20. It is known, however, that such alloy is difficult to cast in the amorphous form and tends to be unstable. The addition of silicon and/or carbon to such iron-boron alloy has permitted the rapid casting of strip material used for electrical applications. However, a continuing objective in this area is to identify an optimum. alloy composition for amorphous strip for electrical applications.
Minor differences in chemical composition may have significant effects on the castability of amorphous strip material and on the magnetic, physical and electrical properties of such strip. Therefore, an optimum alloy composition for amorphous strip material for use in electrical applications is desired in the strip casting art.
Numerous alloys and alloy ranges for amorphous materials are disclosed in the prior art. For example, U.S. Pat. No. 3,297,436 discloses amorphous alloys of gold-silicon, silver-copper, silver-germanium, and palladium-silicon among others. The patentee, Professor Pol E. Duwez, recognized that the amorphous product may inter alia, have improved properties including improved electronic and magnetic properties when compared to conventional alloys. U.S. Pat. No. 3,856,513 discloses an extremely broad composition for amorphous metal alloys under the general formula M60-90Y10xe2x80x9430Z0.1xe2x80x9415 where M is iron, nickel, chromium, cobalt, vanadium or mixtures thereof, Y is phosphorus, carbon, boron, or mixtures thereof, and Z is aluminum, silicon, tin, antimony, germanium, indium, beryllium and mixtures thereof.
With regard to specific Developments in the area of amorphous metal alloys having improved magnetic properties, the patents noted below may also be of interest.
U.S. Pat. No. 4,056,411 pertains to alloys for magnetic devices with low magnetostriction including 3-25% iron and 7-97% cobalt. U.S. Pat. No. 4,134,779 discloses an iron-boron ferromagnetic alloy with high saturation magnetization. U.S. Pat. No. 4,150,981 relates to an iron-nickel-cobalt-boron alloy having high saturation induction and near zero magnetostriction. U.S. Pat. No. 4,154,144 discloses various alloys, none of which contain silicon, which are said to possess high permeability, low magnetostriction, low core loss, and high thermal stability. U.S. Pat. No. 4,154,147 discloses an iron-boron glassy magnetic alloy which contains 2-10% beryllium, and U.S. Pat. No. 4,190,438 pertains to an iron-boron-silicon magnetic alloy which contains 2-20% ruthenium. U.S. Pat. No. 4,197,146 discloses an amorphous metal consisting of aligned flakes of a particular alloy composition. U.S. Pat. No. 4,217,135 relates to an iron-boron-silicon alloy with a high crystallization temperature and low coercivity. U.S. Pat. No. 4,219,355 pertains to an Fe80-82B12.5xe2x80x9414.5Si2.5-5.0C1.5-2.5 alloy composition. Such developments in the art shows that optimization of alloy compositions of amorphous strip material, such as for electrical applications, is a continuing objective in the art of rapid solidification of amorphous strip materials.
The present invention may be summarized as providing a novel amorphous metal alloy strip having a width greater than about one inch and a thickness less than about 0.003 inch. The alloy of the present invention consists essentially of 77 to 80 atomic percent iron, 12 to 16 atomic percent boron and 5 to 10 atomic percent silicon with no more than incidental impurities. This narrow composition for the strip material of the present invention, which is not disclosed or suggested as an optimum alloy by the prior art, is characterized by a 60 cycle per second core loss of less than about 0.100 watts per pound at 12.6 kilogauss, saturation magnetization. of at least 15 kilogauss, and a coercive force of less than about 0.04 oersteds. Such alloy is also characterized by increased castability, and the strip produced therefrom exhibits at least singular ductility, as defined below. A method of producing such ductile strip material is also provided wherein a continuous stream of molten metal consisting essentially of 77 to 80 atomic percent iron, 12 to 16 atomic percent boron and 5 to 10 atomic percent silicon, is delivered through a slot in a nozzle, the slot having a width of at least .010 inch, and onto a casting surface disposed within 0.120 inch of the nozzle and moving past the nozzle at a speed of 200 to 10,000 linear surface feet per minute, solidifying the strip on the casting surface and separating the strip from the casting surface.
Among the advantages of the present invention is the provision of an amorphous strip material having a unique, narrow range of iron, boron and silicon, which makes the strip material particularly advantageous for electrical applications such as in distribution transformers, and the like.
A particular objective of this invention is the identification of an alloy composition for predominately amorphous strip material which exhibits excellent magnetic properties, especially in terms of minimized core loss values, which makes such strip useful for electrical applications.
In addition to the beneficial magnetic and electrical properties of the strip of the present invention, another objective is to provide an alloy composition which is able to be rapidly quenched and solidified from the molten state into strip form with a high degree of castability. The ductility and physical integrity of the resultant cast strip is found to be particularly advantageous.